Question

how to factorise and solve -x^2 - 8

Answer 1

8 isn't a perfect square, so that can't be factored without using radicals.
As for solving it, is that equal to something?

Answer 2

that's what I thought but I've got to draw it as a graph

Answer 3

there's y= (x-2)(x+2)(x+2) and y= -x^2 -8

Answer 4

I've only got to sketch it but I need the x intercept I think

Answer 5

so you need to sketch both of those and find the solution/intersection point?

Answer 6

Yep

Answer 7

ok. for the first one you can use the x-intercepts.
The second one, doesn't have x-intercepts. You can draw it using transformations. Reflect the parabola over the x-axis and shift it down 8.

Answer 8

Ooh I see yes that's clever!

Answer 9

:)
You can solve this algebraically as well
\((x-2)(x+2)(x+2)=-x^2-8\)
\((x^2-4)(x+2)=-x^2-8\)
\(x^3+2x^2-4x-8=-x^2-8\)
\(x^3+3x^2-4x=0\)

Answer 10

Okay thankyo uvery much

Answer 11

you're welcome